We have previously demonstrated that although serum high density lipoprotein (HDL) increases in rats fed alcohol for up to 7 wks, HDL particles of the alcohol-fed rats are deficient in apolipoprotein (apo) E when compared with those isolated from rats pair-fed the alcohol-free control diet. Epidemiological studies have shown that serum HDL levels are negatively correlated with incidences of atherosclerotic heart disease. HDL plays an important role in reverse cholesterol transport. We have found that apo E-deficient HDL particles from alcohol-fed rats was bound less well with hepatic membranes compared to normal apo E of control rats due to lower contents in apo E. We plan to continue our effort in studying the effects of ethanol on the synthesis and secretion of apolipoproteins by hepatocytes and to test several new hypotheses. We hypothesize that: a) apo E-deficient HDL particles originating from hepatocytes are brought about by improper assembly or abnormal secretion of HDL caused by alcohol exposure, b) apo E-deficient HDL particles are more resistant to degradation but yet more apt to deliver cholesterol to the liver for disposal, c) the ability of apo E-deficient HDL to function in reverse cholesterol transport is altered, and d) alcohol drinking affects many functions of macrophages in lipoprotein metabolism and thus interfere with reverse cholesterol transport. We will also carry out studies in humans in order to compare with results in rats. Specific aims of this proposal include: 1) to study the effect of alcohol on the synthesis and secretion of apolipoproteins and their MRNA levels in rat hepatocytes, 2) to compare the uptake of HDL particles isolated from alcohol-fed and control rats by the liver and their ability to function as the cholesterol donor for the live cells, 3) to compare the abilities of HDL particles isolated from the alcohol-fed and the control rats to function as the cholesterol acceptor from cholesterol-loaded macrophages, 4) to study the effects of alcohol on cholesterol loading in peritoneal macrophages and Kupffer cells and on their ability to synthesize and secrete apo E in response to cholesterol loading, 5) to study the effect of alcohol drinking on the apolipoprotein profiles of serum and HDL in human in order to compare with results in rats. We seek to understand how moderate alcohol consumption affects serum lipoprotein an how these changes lead to protection against atherosclerotic heart disease.